A key element in the driveline and drive train of a rear-wheel drive vehicle is a power transfer mechanism called a fixed axle. The fixed axle combines transmission and differential in a single unit.
In rear-wheel drive systems used on vehicles, the drive train is compacted into an engine/transmission/propshaft/fixed axle/driving axle “package” that provides torque force to the rear wheels.
The main purpose of the driving axles is to transmit engine torque from the final drive unit to the rear wheels. As part of the driving axle assembly, the constant velocity joints (“CV joints”) are designed to operate at various angles to accommodate up and down movement of the rear wheels. Some CV joints also permit shaft length changes caused by up-and-down movement of the rear wheels and by fixed axle movement due to torque reaction.
The driving axle typically has CV joints at both “inboard” and “outboard” ends. The inboard CV joint generally consists of an outer race and stub shaft, an inner race, a cage, ball bearings, and a ball retainer. The outer race is called a “plunge” type because it has elongated grooves which allows the bearing cage and bearings to slide in and out as the front wheels go up and down. The inboard CV joint stub shaft is splined to the differential side gear.
The outboard CV joint generally consists of an outer race, a cage, an inner race, and ball bearings. The CV joint outer race stub shaft is splined to accommodate a splined hub that is pressed on and held by a staked nut. Typically, this is referred to as a ball-type fixed CV joint.
These CV joints use the rolling ball bearings in curved grooves to obtain uniform motion. The balls, which are the driving contact, move laterally as the joint rotates. This permits the point of driving contact between the two halves of the coupling to remain in a plane that bisects the angle between the two shafts.
One problem with an optimized small angle CV joint is that they may have the ability for the ball bearings to fall out if the CV joint is over articulated prior to assembly into a vehicle. Another similar problem could occur when the CV joint is disassembled. If one or more of the ball bearings is lost, the CV joint may not perform properly.
It is thus highly desirable to insert a device into the CV joint that would prevent the overarticulation of the CV joint that would in turn prevent the loss of ball bearings when the driveline is not fully assembled into a vehicle.